<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        body{
            margin: 0;
            padding: 0;
        }
        div{
            width:200px;
            height:100px;
            border:2px solid blue;
        }

        .d1{
            /* float:left;  */
            background-color: red;
        }

        .d2{
            width:250px;
            height:150px;
            background-color: blue;
            /* float:right; */
        }

        .d3{
            width:250px;
            height:150px;
            background-color: yellow;
        }

        .d4{

        }

        li{
            float:left;
        }

        #div1{
            position: absolute;/*将该标签从文档流中取出，后面的标签自动向上补充*/
            top:100px;/*距离上边框有100px*/
            right:50px;/*距离右边框50px*/
        }

        #div2{
            /*将该标签还在文档流中，后面的标签没有移动*/
            position: relative;
            top:200px;
            left:50px;
        }
        .d4 {
            float: right;
        }
    </style>
</head>
<body>

<div class="d1">
    1111
</div>
<!-- 设置顶部边框的颜色 -->
<div class="d2">
    2222
</div>
<div class="d3">
    3333
</div>

<div class ="d4">4444</div>
<hr>
<div>
    <ul>
        <li>aaa</li>
        <li>bbb</li>
        <li>ccc</li>
    </ul>
</div>
</body>
</html>